Combustion chamber



y 1967 R. DENNIS 3,330,323

COMBUSTION CHAMBER Filed Dec. 17, 1965 United States Patent 3,330,323 COMBUSTION CHAMBER Ralph L. Dennis, Swampscott, Mass., assignor to Boston Machine Works Company, Lynn, Mass, a corporation of Massachusetts Filed Dec. 17, 1965, Ser. No. 514,642 4 Claims. (Cl. 158-1) ABSTRACT OF THE DISCLOSURE The invention hereinafter disclosed comprises the provision of an inclined deflecting surface within the closed end of a combustion chamber of an oil burner to recirculate back to the entering end of the chamber a substantial portion of the air entrained in the stream of air and fuel projected into the chamber toward said closed end.

This invention relates to improvements in inner combustion chambers for use in the fireboxes of boilers or heaters using oil as a fuel. One common form of oil burner consists of an air tube, usually horizontal, which extends into the firebox and delivers a strong stream of air into which is injected a fine spray of fuel oil so that the droplets of the spray are surrounded by air as they emerge from the burner into the flame by which they are consumed. For efiicient and satisfactory operation, a number of factors have to be considered, the chief factor being the correct ratio of fuel to air in the stream delivered into the firebox. It is equally important to supply the minimum amount of air required for complete combustion and to see that none of the air is wasted for if excess air is permitted to go through the system, the result is a smelly fire and lower efiiciency. The volume of the firebox in relation to the rate of fuel consumption is also an important factor. Complete combustion of the fuel with substantially odorless resultant combustion gases is highly desirable, particularly in home-heating installations.

According to the present invention an inner combustion chamber of special shape is provided to be mounted on the end of the air tube which projects into the firebox. For a more complete understanding of the invention, reference may be had to the following description thereof, and to the drawings, of which FIGURE 1 is a sectional View of the lower portion of a boiler in which is mounted a combustion chamber embodying the invention;

FIGURE 2 is a sectional view of a combustion chamber connected to the end of a fire tube;

FIGURE 3 is a section on the line 33 of FIGURE 2; and

FIGURE 4 is an end elevation of the combustion chamber shown in FIGURE 3.

The lower portion of a typical boiler or heater 1!} is shown in FIGURE 1. An air tube 12 extends from a blower 14 outside of the boiler into the firebox 16 of the boiler. Insulation of asbestos rope 18 surrounds the air tube and is enclosed in a steel sleeve 20. Fuel is introduced into the air stream by a nozzle 22 indicated in FIGURE 3.

Secured to the end of the sleeve 20 is a combustion chamber 24 of refractory fibrous material. The chamber 24 can be made by a vacuum casting method which consists of blowing or fiowin air-borne or liquid-borne fibers into a foraminous mold in which the fibers are deposited and felted on the wall of the mold as the air or liquid carrier flows through the pores of the mold. By the use of mold wall areas of different orosities, the wall thickness of the deposited fibers can be locally varied.

The combustion chamber 24 shown on the drawing is 'ice cylindrical with one end closed as at 26, the other end having an aperture 28 in which the discharge end of the air tube 12 fits. Around the aperture 28 is an axially extending'flange 3!} which fits snugly on the end of the sleeve 29 and is firmly clamped thereon by a metal strap 32 having end ears 34 drawn together by a bolt and nut 36. The chamber 24 can be cast in one piece, but to facilitate its introduction into a firebox it is preferred to cast it in two parts, as indicated. The strap 32 secures these parts together at one end, a similar strap 38 being employed for the same purpose at the other end of the chamber. The strap 38 passes around an axial flange 40 which encircles the central portion of the end wall 26 which may be made with extra thickness to withstand the pressure resulting from the combustion of the air and oil mixture directed against it and from the constriction of the strap 33.

The chamber 24 has two discharge ports 42 and 44 in its side walls through which the burning fuel and air escape into the firebox. These ports are shown as elongated rectangular apertures extending nearly the entire length of the side wall and centered slightly above the horizontal median plane of the chamber, but they may be of other shapes if desired.

A particularly important feature of the chamber 24 is the frusto-conical elements 46 and 48 which connect the cylindrical wall of the chamber with the respective ends of the chamber. The slant of the inner surfaces 50 and 52 of the elements 46 and 48 is preferably about 45. The surfaces 59 and 52 need not be strictly conical since a slight concavity of these surfaces will not seriously impair their functioning, but their shape should at least approximate frusto-conical surfaces.

When the burner is operating, a stream of air is discharged from the air tube 12 into the chamber 24. Entrained in this stream are tiny droplets of atomized oil which must first be vaporized and then combined with air in the process of combustion. When this air stream strikes the end wall 26 of the chamber the surface 50 effectively reverses its direction and directs it into the main body of the fire emitting through the ports 42 and 44. Some of the reversed stream flows along the top and bottom interior of the chamber until it reaches the surface 52 which smoothly directs it to merge with the main body of air coming from the air tube 12.

The surface 50 is of particular importance since it is found that if a chamber similar to the chamber 24 but without the frusto-conical elements 46 and 48 is employed, some of the air stream hitting the end Wall of the chamber forms eddies in the angle between the cylindrical wall and the end Wall and causes an appreciable percentage of the air to escape unused through the ends of the ports 42 and 44 nearest to the end wall 26 of the chamber. This lowers the efficiency of the apparatus and provides an objectionably smelly flame. The use of a chamber made with the sloping surfaces 50 and 57 results in the production of a sweet flame devoid of the unpleasant odor which results from combustion wherein some of the supplied air is not used in the combustion process.

I claim:

1. A hollow cylindrical combustion chamber of felted refractory fibers, said chamber having one closed end and two opposed discharge ports in its cylindrical Wall extending nearly the entire length of said wall, the other end having an opening adapted to surround the end of an air-tube, said chamber having a cylindrical inner surface, a plane end surface, and an approximately frusto-conical surface connecting said cylindrical surface and said plane surface whereby to induce a counterflow to said other end of a substantial portion of the air projected from said other end to said closed end.

n 3 a 4 2. A combustion chamber as described in claim 1, said References Cited inner surface thereof having a second approximately UNITED STATES PATENTS frusto-comcal surface at the other end of 1ts cylindrical v Surface. 1,574,839 3/1926 Morse 158-1 3. A combustion chamber as described in claim 1, said 5 312131917 10/1965 Scheppers 1581 chamber being composed of two fibrous parts, and re- FOREIGN PATENTS movable means holding said parts assembled. 985,261 3/1951 France 4. A combustion chamber as described in claim 3, said chamber having an axially extending flange at each end FREDERICK L M ATTESON JR Primary Examiner thereof, said holding means comprising a band encircling 10 each f said e E. G. FAVORS, Asszstant Examiner. 

1. A HOLLOW CYLINDRICAL COMBUSTION CHAMBER OF FELTED REFRACTORY FIBERS, SAID CHAMBER HAVING ONE CLOSED END AND TWO OPPOSED DISCHARGE PORTS IN ITS CYLINDRICAL WALL EXTENDING NEARLY THE ENTIRE LENGTH OF SAID WALL, THE OTHER END HAVING AN OPENING ADAPTED TO SURROUND THE END OF AN AIR-TUBE, SAID CHAMBER HAVING A CYLINDRICAL INNER SURFACE, A PLANE END SURFACE, AND AN APPROXIMATELY FRUSTO-CONICAL SURFACE CONNECTING SAID CYLINDRICAL SURFACE AND SAID PLANE SURFACE WHEREBY TO INDUCE A COUNTERFLOW TO SAID OTHER END OF A SUBSTANTIAL PORTION OF THE AIR PROJECTED FROM SAID OTHER END TO SAID CLOSED END. 